Package javassist.expr

Class ExprEditor

java.lang.Object

javassist.expr.ExprEditor

public class ExprEditor
extends java.lang.Object

A translator of method bodies.

The users can define a subclass of this class to customize how to modify a method body. The overall architecture is similar to the strategy pattern.

If instrument() is called in CtMethod, the method body is scanned from the beginning to the end. Whenever an expression, such as a method call and a new expression (object creation), is found, edit() is called in ExprEdit. edit() can inspect and modify the given expression. The modification is reflected on the original method body. If edit() does nothing, the original method body is not changed.

The following code is an example:

 CtMethod cm = ...;
 cm.instrument(new ExprEditor() {
     public void edit(MethodCall m) throws CannotCompileException {
         if (m.getClassName().equals("Point")) {
             System.out.println(m.getMethodName() + " line: "
                                + m.getLineNumber());
     }
 });
 

This code inspects all method calls appearing in the method represented by cm and it prints the names and the line numbers of the methods declared in class Point. This code does not modify the body of the method represented by cm. If the method body must be modified, call replace() in MethodCall.

See Also:

CtClass.instrument(ExprEditor), CtBehavior.instrument(ExprEditor), CtBehavior.instrument(ExprEditor), MethodCall, NewExpr, FieldAccess, CodeConverter

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
(package private) static class	ExprEditor.LoopContext
(package private) static class	ExprEditor.NewOp

Constructor Summary

Constructors

Constructor	Description
ExprEditor()	Default constructor.

Method Summary

Modifier and Type	Method	Description
boolean	doit(CtClass clazz, MethodInfo minfo)	Undocumented method.
(package private) boolean	doit(CtClass clazz, MethodInfo minfo, ExprEditor.LoopContext context, CodeIterator iterator, int endPos)	Visits each bytecode in the given range.
void	edit(Cast c)	Edits an expression for explicit type casting (overridable).
void	edit(ConstructorCall c)	Edits a constructor call (overridable).
void	edit(FieldAccess f)	Edits a field-access expression (overridable).
void	edit(Handler h)	Edits a catch clause (overridable).
void	edit(Instanceof i)	Edits an instanceof expression (overridable).
void	edit(MethodCall m)	Edits a method call (overridable).
void	edit(NewArray a)	Edits an expression for array creation (overridable).
void	edit(NewExpr e)	Edits a new expression (overridable).
(package private) boolean	loopBody(CodeIterator iterator, CtClass clazz, MethodInfo minfo, ExprEditor.LoopContext context)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ExprEditor

public ExprEditor()

Default constructor. It does nothing.

Method Detail

doit

public boolean doit(CtClass clazz,
                    MethodInfo minfo)
             throws CannotCompileException

Undocumented method. Do not use; internal-use only.

Throws:

CannotCompileException

doit

boolean doit(CtClass clazz,
             MethodInfo minfo,
             ExprEditor.LoopContext context,
             CodeIterator iterator,
             int endPos)
      throws CannotCompileException

Visits each bytecode in the given range.

Throws:

CannotCompileException

loopBody

final boolean loopBody(CodeIterator iterator,
                       CtClass clazz,
                       MethodInfo minfo,
                       ExprEditor.LoopContext context)
                throws CannotCompileException

Throws:

CannotCompileException

edit

public void edit(NewExpr e)
          throws CannotCompileException

Edits a new expression (overridable). The default implementation performs nothing.

Parameters:

e - the new expression creating an object.

Throws:

CannotCompileException

edit

public void edit(NewArray a)
          throws CannotCompileException

Edits an expression for array creation (overridable). The default implementation performs nothing.

Parameters:

a - the new expression for creating an array.

Throws:

CannotCompileException

edit

public void edit(MethodCall m)
          throws CannotCompileException

Edits a method call (overridable). The default implementation performs nothing.

Throws:

CannotCompileException

edit

public void edit(ConstructorCall c)
          throws CannotCompileException

Edits a constructor call (overridable). The constructor call is either super() or this() included in a constructor body. The default implementation performs nothing.

Throws:

CannotCompileException

See Also:

edit(NewExpr)

edit

public void edit(FieldAccess f)
          throws CannotCompileException

Edits a field-access expression (overridable). Field access means both read and write. The default implementation performs nothing.

Throws:

CannotCompileException

edit

public void edit(Instanceof i)
          throws CannotCompileException

Edits an instanceof expression (overridable). The default implementation performs nothing.

Throws:

CannotCompileException

edit

public void edit(Cast c)
          throws CannotCompileException

Edits an expression for explicit type casting (overridable). The default implementation performs nothing.

Throws:

CannotCompileException

edit

public void edit(Handler h)
          throws CannotCompileException

Edits a catch clause (overridable). The default implementation performs nothing.

Throws:

CannotCompileException